1. Field of the Invention
The present invention relates to an apparatus for automatically and successively assembling ink ribbon feeder roller assemblies of ink ribbon cassettes that are widely printing units of word processors, typewriters and printers.
2. Description of the Prior Art
Word processors and typewriters incorporate printing units, and personal computers connect printers thereto. The printing units and printers generally involve ink ribbon cassettes which accommodate folded endless ink ribbons.
An example of such ink ribbon cassettes is shown in FIG. 6. A cassette case 80 has a ribbon space 81. A primary roller assembly 82 and a follower roller assembly 83 are disposed to face each other at one side of the ribbon space 81. An endless ink ribbon 100 is regularly folded and received in the ribbon space 81. The roller assemblies 82 and 83 hold the ink ribbon 100 between them and feed the same in a direction indicated with an arrow mark.
In FIG. 7(a), the primary roller assembly 82 comprises a shaft 84, flanges 85a and 85b formed at each end of the shaft 84, a central large diameter portion 86, and a pair of circumferential grooves 87a and 87b formed between the flanges 85a and 85b and the central large diameter portion 86. Ring-shaped rollers 90a (FIG. 6) and 90b are fitted to the grooves 87a and 87b, respectively. The rollers 90a and 90b are made of elastic material such as porous synthetic resin and foam rubber. A solid operation shaft 88 extends from the flange 85a at one end of the primary shaft 84. When assembled, the operation shaft 88 protrudes from the cassette case 80. By slightly turning the operation shaft 88 in a clockwise direction in FIG. 6, slack of the ink ribbon 100 can be removed. Opposite to the operation shaft. 88, the primary shaft 84 has a hollow shaft 89 into which a driving shaft (not shown) of a printer carriage is inserted. According to rotations of the driving shaft, the primary shaft 84 is rotated in a clockwise direction in FIG. 6.
In FIG. 7(b), the follower roller assembly 83 has a similar structure as that of the primary roller assembly 82. The follower roller assembly 83 is substantially axially symmetrical with respect to its central large diameter portion 93. A follower shaft 91 has flanges 92a and 92b at each end thereof. Rotary shafts 95a and 95b, each which has a small diameter extend outwardly from the flanges 92a and 92b, respectively. As shown in FIG. 6, a plate spring 96 pushes support arms 97 toward the primary roller assembly 82. The support arms 97 have through holes into which the rotary shafts 95a and 95b are inserted, respectively. In this way, the follower roller assembly 83 is supported by the support arms 97. Similar to the primary roller assembly 82, the follower roller assembly 83 has circumferential grooves 94a and 94b to which rollers 90c (FIG. 6) and 90d are fitted respectively. The rollers 90c and 90d are pressed against the rollers 90a and 90b of the primary roller assembly 82 to hold the ink ribbon 100 between them.
When the primary shaft 84 is driven, the follower shaft 91 is rotated in a counterclockwise direction in FIG. 6 to feed the ink ribbon 100 in the direction indicated with the arrow mark.
In FIGS. 7(a) and 7(b), the grooves 87a and 87b of the L primary shaft 84 and the grooves 94a and 94b of the follower shaft 91 have the same diameter, and the rollers 90a, 90b, 90c and 90d fitted to the grooves are identical to each other. If required, the primary shaft 84 and follower shaft 91 may have grooves of different diameters, and in this case, rollers fitted to the grooves may have different diameters.
Conventionally, the roller assemblies mentioned above are manually assembled. With the help of elasticity of the rollers, the rollers are pushed beyond the flanges 85a, 85b, 92a and 92b and fitted to the grooves 87a, 87b, 94a and 94b. This manual work takes time and manpower, and therefore, it is desirable to provide an apparatus that can automatically and successively assemble the roller assemblies.